From 8509117a12cf9781b7b0ba40f4fc4145d7338438 Mon Sep 17 00:00:00 2001
From: Derek Collison <derek@nats.io>
Date: Wed, 10 Jul 2019 21:07:09 -0700
Subject: [PATCH] Allow sync subs to allow m.Respond with auto-unsub

Signed-off-by: Derek Collison <derek@nats.io>
---
 nats.go          | 26 +++++++++++++++-----------
 test/sub_test.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 11 deletions(-)

diff --git a/nats.go b/nats.go
index 4b3cfb3c4..ee2ca0cf1 100644
--- a/nats.go
+++ b/nats.go
@@ -2904,7 +2904,6 @@ func (nc *Conn) removeSub(s *Subscription) {
 	s.mch = nil
 
 	// Mark as invalid
-	s.conn = nil
 	s.closed = true
 	if s.pCond != nil {
 		s.pCond.Broadcast()
@@ -2941,7 +2940,7 @@ func (s *Subscription) IsValid() bool {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	return s.conn != nil
+	return s.conn != nil && !s.closed
 }
 
 // Drain will remove interest but continue callbacks until all messages
@@ -2966,8 +2965,12 @@ func (s *Subscription) Unsubscribe() error {
 	}
 	s.mu.Lock()
 	conn := s.conn
+	closed := s.closed
 	s.mu.Unlock()
-	if conn == nil {
+	if conn == nil || conn.IsClosed() {
+		return ErrConnectionClosed
+	}
+	if closed {
 		return ErrBadSubscription
 	}
 	if conn.IsDraining() {
@@ -3023,8 +3026,9 @@ func (s *Subscription) AutoUnsubscribe(max int) error {
 	}
 	s.mu.Lock()
 	conn := s.conn
+	closed := s.closed
 	s.mu.Unlock()
-	if conn == nil {
+	if conn == nil || closed {
 		return ErrBadSubscription
 	}
 	return conn.unsubscribe(s, max, false)
@@ -3199,7 +3203,7 @@ func (s *Subscription) Pending() (int, int, error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.conn == nil {
+	if s.conn == nil || s.closed {
 		return -1, -1, ErrBadSubscription
 	}
 	if s.typ == ChanSubscription {
@@ -3215,7 +3219,7 @@ func (s *Subscription) MaxPending() (int, int, error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.conn == nil {
+	if s.conn == nil || s.closed {
 		return -1, -1, ErrBadSubscription
 	}
 	if s.typ == ChanSubscription {
@@ -3231,7 +3235,7 @@ func (s *Subscription) ClearMaxPending() error {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.conn == nil {
+	if s.conn == nil || s.closed {
 		return ErrBadSubscription
 	}
 	if s.typ == ChanSubscription {
@@ -3256,7 +3260,7 @@ func (s *Subscription) PendingLimits() (int, int, error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.conn == nil {
+	if s.conn == nil || s.closed {
 		return -1, -1, ErrBadSubscription
 	}
 	if s.typ == ChanSubscription {
@@ -3273,7 +3277,7 @@ func (s *Subscription) SetPendingLimits(msgLimit, bytesLimit int) error {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.conn == nil {
+	if s.conn == nil || s.closed {
 		return ErrBadSubscription
 	}
 	if s.typ == ChanSubscription {
@@ -3293,7 +3297,7 @@ func (s *Subscription) Delivered() (int64, error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.conn == nil {
+	if s.conn == nil || s.closed {
 		return -1, ErrBadSubscription
 	}
 	return int64(s.delivered), nil
@@ -3309,7 +3313,7 @@ func (s *Subscription) Dropped() (int, error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.conn == nil {
+	if s.conn == nil || s.closed {
 		return -1, ErrBadSubscription
 	}
 	return s.dropped, nil
diff --git a/test/sub_test.go b/test/sub_test.go
index bbd3882e8..abc7ef723 100644
--- a/test/sub_test.go
+++ b/test/sub_test.go
@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nuid"
 )
 
 // More advanced tests on subscriptions
@@ -1495,5 +1496,37 @@ func TestSubscriptionTypes(t *testing.T) {
 	if _, _, err := sub.PendingLimits(); err == nil {
 		t.Fatalf("We should NOT be able to call PendingLimits() on ChanSubscriber")
 	}
+}
+
+func TestAutoUnsubOnSyncSubCanStillRespond(t *testing.T) {
+	s := RunDefaultServer()
+	defer s.Shutdown()
+
+	nc := NewDefaultConnection(t)
+	defer nc.Close()
+
+	subj := nuid.Next()
+	sub, err := nc.SubscribeSync(subj)
+	if err != nil {
+		t.Fatalf("Error susbscribing: %v", err)
+	}
+	// When the single message is delivered, the
+	// auto unsub will reap the subscription removing
+	// the connection, make sure Respond still works.
+	if err := sub.AutoUnsubscribe(1); err != nil {
+		t.Fatalf("Error autounsub: %v", err)
+	}
+
+	inbox := nats.NewInbox()
+	if err = nc.PublishRequest(subj, inbox, nil); err != nil {
+		t.Fatalf("Error making request: %v", err)
+	}
 
+	m, err := sub.NextMsg(time.Second)
+	if err != nil {
+		t.Fatalf("Error getting next message")
+	}
+	if err := m.Respond(nil); err != nil {
+		t.Fatalf("Error responding: %v", err)
+	}
 }